Booking reliability · guide
How to prevent double booking
Protect each booking at the database boundary, account for duration and buffers, revalidate on submission and test concurrency.
Reviewed for technical accuracy, practical usefulness and product neutrality.
Author: TapFlow Editorial · Reviewed by: TapFlow product teamWhy double bookings happen
Two clients can receive the same availability result, then submit seconds apart. A client-side disabled button cannot coordinate those independent requests.
Protect the full occupied interval
Conflict logic must compare start, duration and any preparation or cleanup buffers. Matching only identical start times allows overlapping appointments of different lengths.
Validate and create atomically
The final availability check and insert should occur in one database-controlled operation or transaction. If another booking wins first, the second request receives a clear conflict and fresh alternatives.
Define which statuses block time
Confirmed and pending bookings may block availability, while cancelled bookings should release it. The policy must be explicit and applied consistently to the calendar and API.
Test the race, not only the happy path
Send two booking requests for the same interval concurrently. Exactly one should succeed. Repeat across staff, services, time zones, rescheduling and cancellation.
Frequently asked questions
Is hiding booked times enough?
No. It improves the interface but cannot prevent concurrent requests. The server and database must enforce the rule.
Should cancelled bookings release the slot?
Usually yes, according to the business policy. The status transition and availability update must be handled consistently.